The present invention relates generally to implantable medical devices, and more specifically to an apparatus and method for treating breathing disorders.
When properly functioning, the diaphragm maintains a respiration rate of about 10-50 breaths per minute. A variety of ailments can cause a person not to breathe properly. One such disorder is central sleep apnea, which occurs when the brain fails to send the appropriate message to the muscles responsible for initiating the respiratory cycle. This causes brief interruptions of breathing during sleep. Treatment of central sleep apnea is important because it may be associated with irregular heartbeat, high blood pressure, heart attack, and stroke.
Another breathing disorder is Cheyne-Stokes respiration, which is characterized by a cycle of rapid, deep breathing followed by apneic episodes. Other patients suffer from intractable hiccups, which are chronic and uncontrollable. Also, there are many respiratory problems which are related to patients who have paralysis and are unable to breath on their own.
One method of treating such respiratory problems is phrenic nerve pacing, which is also called diaphragmatic pacing. The phrenic nerve is generally known as the motor nerve of the diaphragm. It runs through the thorax, along the heart, and then to the diaphragm. Diaphragmatic pacing is the use of electronic stimulation of the phrenic nerve to control the patient""s diaphragm and induce a respiratory cycle. In the past, this has been accomplished by surgically placing a nerve cuff on the phrenic nerve, and then delivering an electric stimulus. The electric stimulus of the phrenic nerve then causes the diaphragm to induce a respiratory cycle. One problem associated with this method is that nerve cuff surgery can be quite invasive and it runs the risk of nerve damage. Another problem with the phrenic nerve cuff method is that nerve cuffs are a relatively undeveloped technology.
Another problem facing respiratory patients is that many also suffer from heart problems which require heart pacing. If the patient chooses to receive diaphragmatic pacing therapy and heart pacing therapy, the patient is required to have two independent stimulation systems implanted in their bodies. This increases the risk of complications both during and after surgery.
Thus, there is a need for a system which provides reliable and safe phrenic nerve pacing, and also permits a physician to incorporate heart pace management and diaphragmatic pace management into a single implantable pace management system.
The present system provides a method and apparatus for performing diaphragmatic pacing. In one embodiment, a pacing lead is situated in or near a patient""s heart so that the electrode on the lead is situated to deliver an electric stimulus to the patient""s phrenic nerve when the need for it is determined by a controller.
In further embodiments, the present system is applicable for treating respiratory ailments such as sleep apnea. The system provides for sensing a physiological state of the patient related to respiration effort using an electrode implanted in the heart. When a physiological state indicating a need for therapy is detected, an electrical stimulus is triggered by a controller, and the electrode delivers an electric stimulus to the phrenic nerve, initiating a respiratory cycle. In another embodiment, when a physiological state indicating a respiratory event is detected, the controller inhibits delivery of an electrical stimulus, which is programmed to be delivered at a predetermined rate.
In a further embodiment, the system includes a system for pacing both the patient""s diaphragm and their heart. This system includes inserting a lead into the patient""s body so that an electrode is situated to stimulate both the heart and the phrenic nerve. Two different stimuli voltages are deliverable. A first at an amplitude which is higher than the cardiac stimulation threshold but lower than the diaphragm pacing threshold, and a second, more powerful, stimulus at a level which stimulates both the heart and diaphragm at the same time.
Some of the advantages of the present system are that it provides diaphragmatic pacing using the advanced, developed technology provided by modern cardiac pacing lead technology. It also provides phrenic pacing without the invasive surgery associated with attaching nerve cuffs. Furthermore, it provides concurrent heart pacing and diaphragm pacing using one implanted system instead of two.